This proposal seeks to be a participating clinical center (PCC) in the RFA entitled "Polycystic Kidney Disease: Innovate Imaging Techniques." ADPKD is the most common inherited and renal disease accounting for 4% of the ESRD population in the U.S.A. Therapies aimed at slowing or halting the progression of renal failure in human ADPKD have not been successful. Given the slow pace of ADPKD, it is important to identify individual at high risk for progression to ESRD and surrogate markers early in the course of the disease so that potentially helpful interventions can be tested. This site intends to measure the rate of progression of renal disease in ADPKD subjects with normal renal function at high risk (including Afro-American race) as compared to matched ADPKD patients at low risk for progression to ESRD. Specifically, it will be determined if disease progression should be measured by change in renal cyst and parenchyma volume measured by magnetic resonance imaging as compared to change in glomerular filtration rate in either group. It will be determined if different patterns of change in renal cyst and parenchyma volume occur in ADPKD individuals at high as opposed to low risk for progression; e.g., increased renal parenchyma may predominate in high risk individuals. Renal volume increases in ADPKD children in excess of normal renal growth, however, the characteristics of renal structural change in ADPKD children is not understood with regard to cystic and parenchymal growth and echogenicity. Relative changes over time may be important in predicting disease outcome. This study will characterize APDKD children in comparison to unaffected, unrelated children where normal renal growth is occurring using both ultrasound and magnetic resonance imaging to address these questions. This study will provide new information with regard to the radiographic characteristics of disease progression in APDKD, increase understanding of the processes involved early in renal disease progression, provide accurate measurement of makers of disease progression early in ADPKD, and provide genetic, phenotypic and radiographically well characterized patients who will benefit most from therapeutic intervention.